Abstract The study investigates the significance of the deformation capacity of bolts in bolted bearing lap connections, focussing on connections with aligned and misaligned bolt holes. The investigation includes a series of tests on S960 steel lap connections with M12 and M16 bolts of different bolt classes to evaluate the effects of misalignment of bolt holes and the ability of the bolts to redistribute forces. The test results of connections with aligned bolt holes show that the deformation capacity of the bolts was sufficient to equalise the bolt forces. However, the test results of connections with misaligned bolt holes indicate a potential reliability issue in the design of lap bolt connections where the ductility condition is not met, especially for high‐strength bolt classes, e.g. 10.9. The connections were characterised by premature failure of the bolt(s) as the deformation capacity of the bolt was used to overcome the misalignment of the bolt holes. These conclusions can be transferred to connections with lower steel grades, such as S235.

Unanchored steel storage tanks, commonly used in industrial facilities, can suffer damage during major earthquakes due to various failures. To better understand the seismic behaviour of such structures, a pushover-based seismic performance assessment of four tanks with varying slenderness ratios was performed. The emphasis was placed on understanding the relationship between engineering demand parameters, tank slenderness ratio, and wall geometrical imperfections, which were, however, imposed only to the lower course around the tank circumference to assess the upper limit of the effect of geometrical imperfections on the elephant-foot buckling (EFB). The findings reveal that axial compressive stress in the tank wall correlates with increased slenderness and geometrical imperfections. This implies that the axial compressive stress in the wall of broader tanks is relatively low, and the bulging at the bottom of the wall is mainly due to high hydrodynamic pressure and the resulting hoop stress. In contrast, the wall of slender tanks buckles primarily due to high axial stresses, leading to EFB. Through dynamic analysis, the study showed that the pushover analysis can underestimate the axial stress if the tank’s base plate is uplifted significantly before EFB occurs. The effect of the impact should thus be considered, especially in the case of slender tanks, because the base plate uplift mechanism is more pronounced than in broader tanks. Further research is needed for a more accurate prediction of the axial compressive stress in slender tanks. However, the safety margin in the post-yielding range is low because the yielding area of the tank wall rapidly increases after the occurrence of steel yielding. In the absence of a detailed 3D model of tanks, simplified formulas for estimating stresses in the tank wall may be used for the broader tanks but not for more slender tanks because of their inability to simulate the highly non-linear relationship between the ground motion intensity and the stresses observed in the plastic region of the tank wall.

Although bolted bearing-type connections are widely used in steel structures, knowledge of their deformation behaviour is limited. Deformation behaviour is particularly important for nominally pinned connections, lap connections and other connections with bolts in bearing. Bolted bearing-type connections are characterised by non-linear deformation behaviour in terms of yielding of the material in front of the bolt hole, which occurs at the beginning of the deformation path due to the embedding of the bolt in the steel plate. The paper deals with the formulation of a non-linear analytical expression that describes the embedding of the bolt and allows the designer to estimate the deformation of the bolt hole due to the bearing. The expression was derived based on numerical analysis and confirmed by tests on bolted lap connections made of mild and high-strength steels. Test results of lap joints with different geometries, number of bolts, steel grades and failure modes are also used to demonstrate the applicability of the prediction model. Comparison to the existing Eurocode linear load-deformation model for bearing is also shown. It is shown that the load-deformation relationship for bearing at bolt holes proposed in this paper, which is already included in the new generation of the Eurocode for the design of joints in steel structures, can predict the load-deformation behaviour well. The bearing resistance limit to control the bearing deformation and a simplified linear load-deformation model based on the proposed non-linear model are also presented.

The forthcoming second generation of EN 1993‐1‐5 is bringing changes in terms of buckling and interpolation curves that allow the positive effects of torsional stiffness of closed‐section stiffeners to be taken into account. Regarding the determination of the critical buckling stress for global plate buckling, analytical or numerical methods may be used. FprEN 1993‐1‐5 provides a simplified analytical equation for determining the critical buckling stress of an equivalent orthotropic plate, which can also be found in the informative Annex A of EN 1993‐1‐5. The given equation does not take into account the torsional stiffness of longitudinal stiffeners with closed cross‐sections. The latter are often used in plated structures due to fabrication and strength benefits. This paper compares two methods for determining the elastic critical plate buckling stress that consider the positive effect of the torsional stiffness of closed‐section stiffeners. First, a newly proposed analytical method that accounts for the torsional stiffness of closed‐section stiffeners is derived on the same basis as the current equation in Annex A. Secondly, a numerical linear buckling analysis is performed on a large number of stiffened panels. The advantages and disadvantages of both methods are pointed out. Finally, both values are used to determine the ultimate resistance of plates and with GMNIA results from previous studies.

Design guidelines are proposed for the calculation of the ultimate resistance of longitudinally stiffened, transversally curved plates subjected to uniform compression. They represent internal plated members of box-girders. The proposed method is in accordance with the Eurocode formalism and follows the effective width concept from EN 1993-1-5. The latter strongly underestimates the resistance of stiffened, curved plates. Therefore, the new method extends the scope of the current European standards from flat to curved plates. A general form of the buckling coefficient is derived for orthotropic shell buckling, which is consistent with the solution for orthotropic buckling of plates according to Annex A, EN 1993-1-5. The method presented combines the new equation with the existing design proposals for unstiffened curved panels from the literature and the current design rules for flat plated structures according to EN 1993-1-5. The method is compared with numerical results on simply supported, cylindrically curved panels stiffened with trapezoidal longitudinal stiffeners, where the longitudinal edges are unconstrained and loaded edges are constrained, and a good correlation is achieved.

Curling failure typically appears in bolted connections with thin plates, where the force is transferred by bolt bearing. The curling phenomena is related to the high compressive stresses caused by bolt bearing, which cause the plates to buckle, reducing the bearing strength of connections. Since the reduction of the bearing strength due to curling is not considered in design codes, the curling phenomenon has been studied numerically to understand the mechanical behaviour and to develop simple design rules that take into account reduction in bearing strength. The reduction factor for reducing the bearing resistance by curling was developed taking into account the Eurocode approach, i.e. by calculating the elastic critical force associated to curling and the relative slenderness. Therefore, the elastic critical force in relation to curling was obtained by parametric buckling analysis in finite element software Abaqus. These results were used to develop a simple analytical model for the calculation of the elastic critical curling force. The reduction factor was obtained from the relationship between the results of parametric GMNIA and relative slenderness. The strength of single bolt connections was determined by geometrical and material nonlinear analysis with imperfections (GMNIA) considering various parameters, namely ratio of the bolt diameter to plate thickness, end distance e 1 , edge distance e 2 , material grade (S235, S690), shape and amplitude of imperfections and boundary conditions. The accuracy of the reduction factor for bearing strength is checked on the basis of experimental data given in literature.

An investigation of bolted connections with a specific geometry and bolt arrangement that require high local ductility to achieve the predicted resistances according to the design rules of the new prEN 1993-1-8 is presented. The experimental campaign includes tensile and shear tests on mild steel coupons to calibrate the parameters used for the true stress-strain relationship, damage initiation criterion and fracture evolution, while a numerical model for the high strength steel grade S690 was selected from the literature. The FEA results were satisfactorily validated by experiments on bolted connections for which the rules of the new prEN 1993-1-8:2021 were used to predict the resistance and deformation behaviour. The deformation behaviour was predicted by applying the new analytical model to calculate the deformation at the bolt hole due to the bearing action. The resistances of the tested connections were also predicted using EN 1993-1-8:2005. It is clearly shown that the new design formulae predict the experimental results significantly better than the results obtained according to EN 1993-1-8:2005. The FEA of a bolt group in bending, representing a high web splice, provides new proof for an analytical model for the distribution of forces between the bolts in the elastic stage and at ultimate resistance. Furthermore, the new Eurocode approach for predicting the bearing deformation behaviour at the bolt hole agreed well with the experimental and numerical results.

In this paper, the stability behaviour of longitudinally stiffened, transversally curved steel plates under uniform compressive stresses is investigated and new design guidelines are proposed to extend the scope of the current European standards for flat plated structures to stiffened curved plates. For this purpose, a numerical model is built in Abaqus, which is verified with own test results and numerical results from the literature. It incorporates geometric imperfections based on the modification of node coordinates using sinusoidal functions, and is further used in a comprehensive parametric study based on nonlinear numerical analysis (GMNIA). The parametric study investigates the effects of curvature, slenderness of the plate, size of stiffeners and shape of initial imperfections on the ultimate resistance of the stiffened curved plates. From the results, some important conclusions are drawn regarding the structural behaviour and the positive effects of curvature on the cross‐sectional resistance. In particular, it is found that stiffened curved plates are less sensitive to the shape of the initial imperfections compared to flat stiffened plates, and the introduction of curvature generally adds a reserve of resistance to the stiffened panel under compressive stresses. Based on numerical results, design rules are proposed for longitudinally stiffened curved plates subjected to compressive stresses. The rules are in accordance with the formalism of EN 1993‐1‐5 for flat plated structures and follow the effective width concept. The maximum loads obtained from numerical analysis are compared with the new design rules and a good correlation is obtained.

This paper investigates the stability behaviour and load carrying capacity of longitudinally stiffened, transversally curved steel plates under compressive stresses. The behaviour of stiffened, curved plates is a complex problem, especially due to the interaction of curvature, relative stiffness of the stiffeners and initial imperfections. A comprehensive parametric study is presented to investigate the effects of curvature, plate slenderness, size and shape of stiffeners on the ultimate resistance of stiffened curved plates. The aim of the study is to explain the behaviour of such structures and to demonstrate the benefits that can be obtained from bridge decks with curved plates. From the results some important conclusions are drawn regarding the structural behaviour and the positive effects of curvature on the cross-sectional resistance. A study on the influence of geometric imperfections on the load-bearing capacity is presented, which is based on the modification of nodal coordinates by means of sine-shape functions.

This paper reports on experiments addressing the buckling and collapse behaviour of pin-ended hot-rolled stainless steel equal-leg angle columns under pure axial compression, aiming to provide reliable experimental data needed to develop explicit design guidelines for hot-rolled stainless steel angle columns currently absent in European standard. The systematic experimental programme included two test groups of specimens with nominal dimensions of 60 ? 60 ? 6 mm and 100 ? 100 ? 10 mm produced from austenitic grade EN 1.4301, and involved tensile material tests, geometric imperfection measurements, residual stress measurements, 6 stub column tests and 20 global compression tests. A wide range of column slenderness ratios was carefully selected to account for both elastic and inelastic failure characteristics including flexural and flexural?torsional modes and the influence of the legs? width-to-thickness ratios. The test setup and procedure together with the key experimental results and characterised failure modes, were fully reported and discussed. The test results were compared with those predicted using the design methods for compressed stainless steel angle columns provided in European and North American standards. It was observed that the specifications offer conservative strength predictions of the tested columns, primarily due to the lower distribution of initial geometric imperfections of tested columns in comparison with the permissible fabrication tolerances that are usually used as the basis of stability checks in codified design.

This paper deals with the experimental and numerical evaluation of the buckling behaviour and ultimate resistance of stiffened transversally curved panels subjected to uniform axial compression. Furthermore, a verification procedure for curved stiffened panels is proposed that gives a good estimation of the maximum loads obtained from experimental and numerical tests. The procedure is in line with the design methodology of EN 1993-1-5, accounting also for panel curvature. Nine large-scale tests were performed on longitudinally and transversally stiffened plates made of high strength steel, namely S500 and S700. They were subjected to compressive stresses up to collapse. The nine specimens comprised of flat and curved plates that differed in material grade and geometric parameters, such as panel thickness, aspect ratio, size and shape of stiffeners. The effects of different parameters on the plate's resistance to pure compression are discussed. Moreover, a numerical model built in the general-purpose code ABAQUS is presented and verified against the test results regarding initial stiffness, ultimate resistance and failure mode. Numerical simulations (FEA), based on the test panel geometry, the measured initial geometric imperfections and elasto-plastic material characteristics from tensile tests, demonstrate very good agreement with experimental results.

The paper is concerned with the statistical analysis of strength functions for bolted connections, namely the bearing resistance, the block tearing resistance, the net cross-section resistance and the resistance of angles in tension connected by a single row of bolts in one leg to obtain partial factors. These strength functions are proposed in the second generation of EN 1993-1-8 and EN 1993-1-1. The statistical analysis is performed using 884 test results available in the background documentation to Eurocode 3 and an additional 380 test results of lap connections with different bolt arrangements, which are available in the literature. A suitable sampling criterion of the test results allowed sufficiently large data sets with a small coefficient of variation, which allowed the assumption of partial factor gamma(M2) - 1.25. EN 1993-1-8 provides the design check of the effective net cross-cross section resistance of angles connected by a single row of bolts in one leg (EN 1993-1-8, 3.103). It is demonstrated that this design check is superfluous and can be completely replaced by the design block tearing resistance, taking into account the design upper limit of the net cross section resistance. (C) 2020 Elsevier Ltd. All rights reserved.

The paper presents test results of one and two bolt connections with very large end distances that failed in bolt bearing, where very high bearing forces were recorded. The purpose of the tests was to investigate the behaviour of the plate in bearing that was not limited by shear, splitting, bolt or net cross-section failure, but with tearing of the material in front of the bolt. The tests showed that the bearing capacity increased insignificantly as the width of the plate increased. Numerical simulations show that bearing resistance is in cases of large end distances significantly influenced by friction forces. They develop because the bolt head and nut, together with the lap plates, constrain the increase of the plate thickness related to plastic deformation. The paper deals with the formation of the stress-strain field as well as the influence of the inner bolt determined by the numerical simulations. The resistances obtained from the tests agree very well with the bearing strength model presented recently by Može and Beg (2014). The coefficient of the bearing strength model that considers the influence of the inner bolt is calibrated on the basis of the presented test results as well as on high strength steel connections with several bolts. The presented bearing strength model was adopted in the final draft of the second generation of EN 1993-1-8.

The paper deals with an extensive experimental study on five stiffened curved plates with different geometry and steel grade. The objective of the study is to analyse the behaviour of curved panels and their longitudinal and transverse stiffeners subjected to pure compression. Before testing, the initial geometric imperfections of the specimens were measured. They will be further used in the finite element model as initial geometry. During tests, the displacement field was measured with photogrammetry. In this paper, some results of the experimental tests are presented together with a study of the effects of different parameters on the element's resistance to pure compression. It is shown that the displacements provided by photogrammetry are in good agreement with those measured with LVDTs in discrete points. The ultimate force of the specimen made of higher steel grade does not differ significantly from other specimens. In addition, there is almost no difference in the resistance between plates with different aspect ratios. Initial imperfections and residual stresses play an important role in the prediction of the stiffened curved plate's response when subjected to pure compression.

The design of full strength bolted beam-to-column beams considering the overstrength factor for the beam material according to EN 1998-1 is particularly demanding, especially in case of heavy beam profiles in combination with higher grade material (e.g. S355). The elastic design of the full strength connection leads to very stocky joint. The component method presented in EN 1993-1-8 that was developed mainly for the design of partial-strength joints may also be used for the design of these connections, but its application is limited mainly to experts. This paper studies bolted beam-to-column joints under monotonic and cyclic loading, particularly hot rolled HEA 600, S355 beam with high bending strength. Two different configurations of bolted connection of HEA 600 to column are studied in order to achieve full strength connection as defined in EN 1998-1, namely eight-bolt rib stiffened and haunched stiffened joint configuration. Both joint configurations are first calculated according to EN 1993-1-8 using component method, where bolt forces and joint bending strength were determined. The first joint is also designed according to the procedure given in ANSI/AISC 385-10. The numerical model, based on this design, was built in FE software Abaqus in order to observe the behaviour under monotonic and cyclic loading. The cyclic loading was defined according to the ECCS and ANSI/AISC 341-10 procedures. The bolt preload was also studied.

ABSTRACTThe paper deals with bolted connections of angles connected by one leg subjected to tension force. These connections are characterized by the eccentricity of the tension force and are dealt with in the EN 1993‐1‐8 standard that provides the design resistance for block tearing, for bolt bearing and for reduced effective net cross‐section that is based on β factors. A closer look on the design resistance of the reduced effective net cross‐section shows that the calculation of β may lead to inconsistencies. An addition of a bolt may lead to decrease of the net cross‐section resistance. Moreover, the formulas for the calculation of the reduced net cross‐section resistances are only a different presentation of the formulas for the block tearing resistance. Analysis of 631 test results from literature shows that the calculation of the block tearing resistance is sufficient and that equations 3.12 and 3.13 of EN 1993‐1‐8 are redundant. The study will also show that a constant distribution of stress on the tension face may be assumed in the formula for the block tearing resistance of the angles connected by one leg in tension (eq. 3.9, EN 1993‐1‐8), similarly to the provisions in American standard AISC 360–05. A modified bolt bearing strength function is also presented and statistically analysed on 631 test results. It is simpler and less conservative than the one in EN 1993‐1‐8.

Bolt bearing is characterized by large plastic deformations that occur mainly near the contact between bolts and plates and may possibly lead to fracture. Numerical modelling of such behaviour is not trivial. The paper focuses on the procedures for numerical analysis that allow numerical modelling of bolt bearing up to fracture. The commercially available software Abaqus software was used for this purpose, taking the advantages of built-in material models and numerical procedures without introducing the user subroutines. The problem of bolt bearing is assessed using static stress analysis, explicit analysis and coupled Eulerian-Lagrange analysis. The fracture model considered is based on stress modified fracture model and relies on the accumulating damage and on the reducing stiffness of finite elements to the point, where they offer no resistance and can be either removed from the model or are left with negligible stiffness. The required parameters (stress triaxiality, equivalent plastic strain to failure and displacement to failure) were determined from the experimental data. A few different bolted connections with different types of failure are analysed with full failure model and the results are compared with experiments. The advantage of Eulerian meshing is considered, where excessive plastic deformations lead to contact problems. Coupled Eulerian-Lagrange analysis with model parts expected to have large deformations were modelled with Eulerian approach and the rest with more conventional Lagrange approach. Diverse material models, element options, time step and their impact on numerical simulation were compared and optimized for speed and accuracy.